The tragedy led to a public outpouring of grief, with tributes to those who lost their lives piled high at the attack sites in the form of bouquets of flowers, hand-written messages, signs, poems and drawings.

It has been a rude awakening for City of Paris archivists who are much more accustomed to handling administrative documents and public records. The project also marks a departure from the response to the attacks on Charlie Hebdo and a kosher supermarket in January. At that time there was no official effort to archive any of the materials from the temporary memorials which those devastating events inspired. Only now Harvard University is undertaking to archive the Charlie Hebdo materials collected by a member of teaching staff who visited Paris in the days following the attacks.

This time a concerted effort is being made to safeguard the artefacts for posterity. Not only do the archivists acknowledge their importance as documents for historical and sociological study but they also recognise the artistic merits of the public contributions. Given the tremendous scale of the task, they have chosen to concentrate their efforts on collecting letters and drawings, which are considered especially valuable in recording that terrible moment in history.

The archivists have been required to tread a fine line between offending sensitivities and losing the artefacts altogether to the street sweeper’s broom. But at what point do the memorials cease to serve their function as a site for public mourning and become rubbish for disposal?

“It’s a day-to-day process, and a contradictory one too, because these memorials are supposed to be ephemeral, but people still need a place to mourn for now,” said Guillaume Nahon, director of the Paris archives.

It is a process which New York State Museum director Mark Schaming is all-too familiar with. Following the September 11 attacks on the World Trade Center, Schaming’s team attempted to strike a delicate balance between allowing members of the public space to grieve and stepping in to safeguard their memorials for posterity.

“You didn’t want to interrupt the life of a memorial while it was still in service… On the other hand, you didn’t want to see it destroyed,” he said.

City of Paris archivists with the assistance of volunteers and cleaning services have already collected thousands of documents from the attack sites.